moult n : periodic shedding of the cuticle in arthropods or the outer skin in reptiles [syn: molt, molting, moulting, ecdysis] v : cast off hair, skin, horn, or feathers; "out dog sheds every Spring" [syn: shed, molt, exuviate, slough]

English

Alternative spellings

• molt (American English)

Noun

1. The process of shedding or losing a covering of fur, feathers or skin etc.

   Some birds change colour during their winter moult.

Translations

• Dutch: rui
• German: Mauser (feathers), Häutung (skin)

Verb

1. To shed or lose a covering of fur, feathers or skin etc.

Translations

• Dutch: ruien
• German: sich mausern (feathers), sich häuten (skin)

In biology, moulting (or molting, also known as shedding or for some species, ecdysis) signifies the manner in which an animal routinely casts off a part of its body (often but not always an outer layer or covering), either at specific times of year, or at specific points in its life-cycle.

Molting can involve the epidermis (skin), hair or fur, or other external layer. In some species, other body parts may be shed, for example, wings in some insects. Examples include old feathers in birds, old hairs in mammals (especially dogs and other canidae), old skin in reptiles, and the entire exoskeleton in arthropods.

Examples

Specific species notes

Birds

In birds, moulting is the periodic replacement of feathers by shedding old feathers while producing new ones. Feathers are dead structures at maturity, and they become gradually worn down and need to be replaced. Adult birds moult at least once a year, though many moult twice, and a few three times. Because feathers make up 4-12 percent of a bird's body weight, it takes a large amount of energy to replace them. For this reason, moults are frequently timed to occur right after the breeding season, but while food is still abundant. The plumage produced during this time is called postnuptial plumage.

Canidae

Dogs and other canids routinely shed their fur twice a year, in the spring and fall.

Seasonal temperature variations influence shedding; some shed all year, some shed specifically twice a year.

Reptiles

The most familiar example of moulting in reptiles is when snakes "shed their skin". This is usually achieved by the snake rubbing its head against a hard object, such as a rock (or between two rocks) or piece of wood, causing the already stretched skin to split. At this point, the snake continues to rub its skin on objects, causing the end nearest the head to peel back on itself, until the snake is able to crawl out of its skin, effectively turning the molted skin inside-out. This is similar to how you might remove a sock from your foot by grabbing the open end and pulling it over itself. The snake's skin is often left in one piece after the moulting process. Conversely, lizards' skins fall off in pieces.

Arthropods

In arthropods, such as insects, arachnids and crustaceans, moulting is the shedding of the exoskeleton (which is often called its shell), typically to let the organism grow. This process is called ecdysis. Ecdysis is necessary because the exoskeleton is rigid and cannot grow like skin. The new exoskeleton is initially soft but hardens after the moulting of the old exoskeleton.

References